x = int(input())


def f(x):
    hx = x // 2
    pw = 1
    for i in range(hx):
        pw *= 26
        pw %= 998244353
    return hx * pw * 25


if x % 2 == 0:
    print(
        f(x) % 998244353
    )
else:
    # 奇数情况
    print(
        f(x - 1) * 26 % 998244353
    )
